The subject matter disclosed herein relates generally to wind turbines and, more particularly, to a method and apparatus for operating a wind turbine during a fault.
Known wind turbines convert the kinetic energy of wind into electrical energy. Wind turbines include one or more blades that rotate when oncoming wind strikes the blades. The flow of wind over the wind turbine blades generates lift, induces rotation, and provides torque to generate power.
At least some known wind turbines include a plurality of controllers within the wind turbine that communicate with each other to control internal components of the wind turbine. Such controllers may include, for example, a pitch controller and a wind turbine controller. Known pitch controllers change a pitch angle of the wind turbine blades. More specifically, known pitch controllers may drive the blades to a desired operating pitch angle based on existing wind conditions, to facilitate enhanced operation. The pitch controller may also rotate the blades to a non-operating, or feathered, position to facilitate reducing the amount of lift induced to the blades from the wind where a major surface of the blade is generally perpendicular to the wind. The blades may be feathered to facilitate preventing damage to the wind turbine, for example, during high wind conditions or during wind turbine fault conditions.
Known wind turbine controllers may function as a master controller for the wind turbine system. For example, a known wind turbine controller may be programmed to control other controllers coupled within the wind turbine, such as the pitch controller. In such configurations, the wind turbine controller issues commands or control messages to the other controllers, and the other controllers implement these commands or control messages on the components subject to their control. For example, the wind turbine controller may issue commands to the pitch controller to pitch the blades to a defined position.
However, wind turbine controllers, such as pitch controllers and wind turbine controllers, may suffer from periodic faults. These faults often arise from losses of communication or other errors in the controllers. The occurrence of such faults may cause undesirable consequences. For example, in one known wind turbine, when a fault occurs, the wind turbine enters a fault state in which a hard braking procedure is implemented and the rotor blades are stopped via mechanical braking and/or through battery-driven braking procedures. Such procedures may induce an undesirable amount of loading upon the wind turbine system and over time, may reduce the operating life of the wind turbine. Moreover, such procedures also cause the wind turbine to operate at a reduced electrical output, with no electrical output, and/or with a reduced operating efficiency. Such procedures thus result in lost and/or reduced revenue generation.